This is intended say that I'll be using mirrors of the "main" method of a different library. Any alternative way of stating that is welcome.

I'm importing unittest because I change the unittest configuration before running the tests in the main method that is passed as an argument.

I'm sure there is something wrong with async_helper (this is software!), but I have no idea what.

You can write the qualified name of the main method.

But I suspect that you don't know what the name of that method is.

You should not use mirrors, @­MirrorsUsed, and pkg/unittest to test isolates. What you're doing is piling on complexity where it doesn't belong. In addition, dart:mirrors is unstable API which also makes it an inappropriate choice for testing core platform features. The alternative is to remove the dependency on unittest. There is a simple alternative in tests/lib/mirrors.

In this case, I'm using mirrors only to get the URL of the library that contains the test that needs to be run in a different isolate.
I guess I could hardcode that in each test. It'll be more fragile, but breaking would be quickly detected, so it's probably not a problem.

The tests were already written using unittest, some of them with multiple test cases, but I guess I can rewrite them to using package:expect and package:async_helper.